Ion beam processing apparatus and method of operating ion source therefor

ABSTRACT

An ion beam processing apparatus and a method of operating an ion source therefore are provided for reducing the frequency of breakdown due to particles, and for increasing the time that an apparatus can be made available by operating the apparatus in a stable state for a long time and minimizing maintenance operations such as cleaning. A plasma generating gas is introduced into a vacuum chamber formed of a processing chamber and an ion source mounted thereto to produce a plasma from the gas, and an electric field is applied within the vacuum chamber to extract ions within the plasma as an ion beam. The ion source comprises an arc power supply, an acceleration power supply for applying a positive potential to the acceleration electrode in order to extract an ion beam, and a deceleration power supply for applying a negative potential to the deceleration electrode ion order to prevent ions from flowing into the ion source. When the ion source is operated, the acceleration electrode is first applied with the positive potential, and then the deceleration electrode is applied with the negative potential.

BACKGROUND OF THE INVENTION

The present invention relates generally to an ion beam processingapparatus and a method of operating an ion source therefor, and moreparticularly to a method of operating an ion source to extract, as anion beam, ions within a plasma generated in the ion source for use in anion beam processing apparatus for performing ion beam milling, ion beamsputtering and so on, and a method of operating an ion beam processingapparatus which uses the ion source.

The ion beam processing apparatus employs plus ions which, whenirradiated to collide with a workpiece, cause accumulation of a pluscharge on the surface of the workpiece, so that the ion beam processingapparatus cannot continuously collide a sufficient ion beam against aprocessed site on the workpiece. For this reason, a neutralizer has beenconventionally provided for irradiating the surface of a workpiece withelectrons to maintain the surface of the workpiece in an electricallyneutral state.

The neutralizer is operated to fill a processing chamber which containsa workpiece with electrons prior to the processing on the workpiece suchthat the neutralization on the surface of the workpiece can be startedsimultaneously with the irradiation of an ion beam to the workpiece.

Conventionally, an ion generator typically produces a plasma to generateions when the ion source is started, while the neutralizer produceselectrons within the processing chamber. It is therefore required toprovide a shielding feature for preventing the electrons from flowinginto the ion generator from the processing chamber. Such a shieldingfeature is implemented by initially activating a deceleration powersupply in an ion source to apply a deceleration electrode with anegative voltage, and subsequently activating an acceleration powersupply to apply an acceleration electrode with a positive voltage.

However, when an ion source operating method as mentioned above isapplied to the ion beam processing apparatus, particles possiblyattached on the electrodes of the ion source to form short-circuitingbetween the acceleration electrode and the deceleration electrode wouldcause repeated breakdowns of the deceleration power supply which hasbeen first activated.

The breakdown of the ion source power supply mainly results from theshort-circuiting between the electrodes of the ion source due toparticles attached thereon. Such particles are in most caseselectrically conductive materials which are sputter deposits onceattached on and coming off of a wall surface within the processingchamber. When the acceleration electrode and the deceleration electrodeof the ion source are applied with respective voltages with suchparticles attached on portions of these electrodes, the two electrodesare short-circuited to cause a sequence of repeated operations involvinga short-circuit current flowing into the ion source power supply, theion source power supply being shut down in response to a detectedexcessive current, and the voltage applied again after a predeterminedtime period. This sequence of operations will be repeated until theparticles causing the short-circuiting are burnt away or removed fromthe electrodes by the short-circuiting current.

Typically, in the ion source power supplies, the acceleration powersupply is designed to have a larger current capacity than thedeceleration power supply. For example, an ion source power supplies maybe a combination of an acceleration power supply having a maximum outputof 1.3 kv, 3 A and a deceleration power supply having a maximum outputof 500 v, 0.2 A. This is because the acceleration and deceleration powersupplies need not have the same capacity in view of the optimization forthe configuration of the entire ion source power supplies. Morespecifically, the acceleration power supply is required to supply an ionbeam current when an ion beam is extracted, whereas the decelerationpower supply hardly has to supply a current for the ion beam.

In addition, values for detecting excessive currents of the respectivepower supplies are typically set in proportion to the rated maximumcurrent values of the respective power supplies, so that the excessivecurrent detection functions at a lower excessive current for a powersupply having a smaller current capacity. Thus, if particles areattached on portions of the electrodes of the ion source, ashort-circuiting current flows through particles when a decelerationvoltage is applied, and activates the excessive current detection in thedeceleration power supply to once shut down the deceleration powersupply. Then, in a predetermined time period, the deceleration voltageis again applied. This sequence of operations is repeated to keep theacceleration power supply from activating indefinitely.

Further, with particles of small size, a short-circuiting currentflowing through such particles results in burning off and consequentlyremoving the particles from the electrodes. However, if particles have acertain large size, a short-circuiting current flowing in thedeceleration power supply having a small capacity is not enough to burnoff the particles which are therefore left on the electrodes, thusforcing the ion source to repeat a sequence of operations involvingexcessive current detection, trip (breakdown) and re-activation.

For the user of these apparatus, it is important to operate theapparatus in a stable state for a long period, minimize maintenanceoperations such as cleaning for the apparatus, and increase an apparatusavailable time resulting from the minimized maintenance operations. Forachieving these objects, it is critical to minimize the frequency of theoccurrence of breakdown, activate the apparatus in a stable state asearly as possible, and maintain the stable operating state.

Generally, the breakdown frequently occurs in the ion source due toparticles attached on the electrodes of the ion source upon powering onthe apparatus after cleaning the inside of the apparatus or aftercleaning the electrodes of the ion source. A conventional method ofoperating the ion source, however, suffers from difficulties in removingparticles, contributing to the breakdown, from the electrodes of the ionsource, and consequent occurrence of repeated breakdowns. To reach astable operating state substantially free from the breakdown, a longtime is required. In some cases, the electrodes of the ion source mustbe frequently cleaned in order to improve such situations, thusexperiencing difficulties in improving the apparatus available time.

SUMMARY OF THE INVENTION

In view of the problems inherent to the prior art as mentioned above, itis an object of the present invention to provide an ion beam processingapparatus and a method of operating an ion source therefor which arecapable of reducing the frequency of the occurrence of breakdown tosmoothly activate the ion source, as well as accomplishing reducedrequirements for maintenance such as cleaning for the electrodes of theion source and so on, a higher reliability of the apparatus, and animproved operating efficiency of the apparatus.

According to the present invention, an ion source is mounted to aprocessing chamber to form a vacuum chamber into which a gas isintroduced to produce a plasma, and an electric field is applied withinthe vacuum chamber to extract ions within the plasma as an ion beam. Theion source comprises an arc power supply, an acceleration power supplyfor applying an acceleration electrode with a positive potential toextract an ion beam, and a deceleration power supply for applying adeceleration electrode with a negative potential to prevent ions fromflowing into the ion source. When the ion source is operated, theacceleration electrode is first applied with a positive potential, andthe deceleration electrode is applied with a negative potential after orsimultaneously with the application of the acceleration electrode withthe positive potential.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating the configuration of an ionbeam processing apparatus according to the present invention;

FIG. 2 is a time chart illustrating an operational procedure accordingto the present invention;

FIG. 3 is a flow diagram illustrating various steps involved in theoperational procedure according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic diagram illustrating the configuration of an ionbeam processing apparatus according to an embodiment of the presentinvention.

Referring specifically to FIG. 1, an ion source, generally designated byreference numeral 1, comprises an acceleration electrode 2 which isapplied with a positive potential; a deceleration electrode 3 which isapplied with a negative potential; an ion source chamber 4; and afilament 5 for emitting thermoelectrons. The illustrated ion beamprocessing apparatus further comprises a filament power supply 6 forheating the filament 5; an arc power supply 7 for producing a plasmawithin the ion source chamber 4; an acceleration power supply 8 forapplying the acceleration electrode 2 with an acceleration voltage forextracting an ion beam; a deceleration power supply 9 for applying thedeceleration electrode 3 with a deceleration voltage for preventingelectrons flowing into the ion source chamber 4 from a processingchamber 11; a controller 10 for operating the respective power supplies6, 7, 8, 9; and the processing chamber 11.

The processing chamber 11 contains a holder 13 for carrying workpieces12; a neutralizer 14 for generating electrons; and a shutter 15 forpreventing an ion beam from being irradiating to the workpieces 12. Theprocessing chamber 11 is externally provided with a power supply 16 forthe neutralizer 14 and a shutter driver 17. The power supply 16 and theshutter driver 17 are controlled by the controller 10.

The ion source 1 is mounted to the processing chamber 11 and used in theform of a vacuum chamber. The controller 10 controls voltages appliedto, currents generated in, and operating timings for the filament powersupply 6, the arc power supply 7, the acceleration power supply 8, thedeceleration power supply 9, the neutralizer power supply 16, and theshutter driver 17.

A conventional operational procedure involves introducing a plasmagenerating gas into the ion source 1; conducting the filament 5 after apredetermined pressure is reached within the ion source 1, andactivating the deceleration power supply 9 to apply the decelerationelectrode 3 with a deceleration voltage. Subsequently, the operationalprocedure proceeds to the activation of the acceleration power supply 8to apply the acceleration electrode 2 with an acceleration voltage, andfinal application of an arc voltage from the arc power supply 7 toproduce a plasma from which an ion beam is extracted. As previouslydescribed, with this operational procedure or method, when thedeceleration electrode 3 is applied with the deceleration voltage withparticles attached on portions of the acceleration electrode 2 and thedeceleration electrode 3 of the ion source, a short-circuiting state isformed between the acceleration electrode 2 and the decelerationelectrode 3 to cause a short-circuiting current to flow into thedeceleration power supply 9, which is detected as an excessive currentto shut down the deceleration power supply 9. Then, after the lapse of apredetermined time, the deceleration power supply 9 is again powered upto apply the deceleration electrode 3 with the deceleration voltage.This sequence of operations is repeated.

FIG. 2 is a diagram for explaining an operational procedure for an ionsource according to the present invention.

As indicated by arrows, this operational procedure involves introducinga plasma generating gas into the ion source 1; conducting the filament 5after a predetermined pressure is reached in the ion source 1; nextactivating the acceleration power supply 8 to apply the accelerationelectrode 2 with an acceleration voltage; subsequently activating thedeceleration power supply 9 to apply the deceleration electrode 3 with adeceleration voltage; and finally applying an arc voltage from the arcpower supply 7 to extract an ion beam.

The foregoing is basic principles and operations of the presentinvention described with reference to the time chart illustrated in FIG.2. In the following, a preferred operational procedure of the presentinvention will generally be described with reference to a flow chartillustrated in FIG. 3.

FIG. 3 is a flow chart illustrating the operation of the controller 10according to the present invention. Referring specifically to FIG. 3, asthe controller 10 starts operating, first at step 30, the shutter driver17 is operated to close the shutter 15 to protect the workpieces 12 frombeing irradiated with ions or electrons from the ion source. Next, atstep 31, a plasma generating gas is introduced into an ion source 4, andthen, the filament power supply 6 is operated to conduct the filament 5,and the arc power supply 7 is forced to supply an arc voltage. Then, atstep 32, the acceleration power supply 8 is operated to supply theacceleration electrode 2 with an acceleration voltage. Next, at step 33,the deceleration power supply 9 is operated to supply the decelerationelectrode 3 with a deceleration voltage. Further, at step 34, theneutralizer power supply 16 is operated to conduct the neutralizer 14 toproduce electrons for neutralizing the surface of the workpiece 12.

With a sequence of the foregoing operations, the ion source is now readyfor activation. Subsequently, at step 35, the shutter driver 17 isoperated to open the shutter 15, followed by proceeding to step 36,where the workpieces 12 are processed.

According to the foregoing operational procedure, with particlesattached on portions of the acceleration electrode 2 and thedeceleration electrode 3, the acceleration power supply 8 having alarger power supply capacity first applies an acceleration voltage toform a short-circuiting state between the acceleration electrode 2 andthe deceleration electrode 3 through the particles to cause ashort-circuiting current to flow from the acceleration power supply 8.The short-circuiting current continues to flow through the particles onthe electrodes 2, 3 until the acceleration power supply 8 stopsoutputting the acceleration voltage in response to the detection of anexcessive current. Since the acceleration power supply 8 has a ratedmaximum current value as high as several amperes, the acceleration powersupply 8 will not trip until the short-circuiting current reaches anexcessive current set value slightly higher than the rated maximumcurrent value, for example, 120% of the rated maximum current value.

In this way, according to the method of operating the ion source of thisembodiment, since the acceleration power supply 8 has a larger powersupply capacity, a larger short-circuiting current can be generated, andaccordingly a time period until an excessive current is detected can bemade longer than the conventional method of operating an ion source.Thus, the particles, causing the short-circuiting between the electrodes2, 3, can be applied with a larger short-circuiting current for a longertime than the conventional operating method. Heat generated by theconducted short-circuiting current causes the particles to heat and burnaway, or the particles are removed from the electrodes by electric shocksuch as discharge or evaporated due to the vacuum environment, thusefficiently eliminating the short-circuiting state between theelectrodes 2, 3.

Further, according to this embodiment, since a larger short-circuitingcurrent can be applied for a longer time by the acceleration powersupply 8 having a large power supply capacity, it is possible to removeparticles in a shorter time if the particles have the same size as wellas to remove particles having a large size which cannot be removed inthe prior art due to an insufficient current. As a result, even if thebreakdown occurred, it could be solved in a shorter time. It is alsopossible to reduce the frequency of maintenance operations such ascleaning for the electrodes of the ion source in order to fix thebreakdown.

In the foregoing embodiment, after the acceleration power supply 8 isactivated to apply the acceleration electrode 2 with an accelerationvoltage, the deceleration power supply 9 is activated to apply thedeceleration electrode 3 with a deceleration voltage. Alternatively, theacceleration power supply 8 and the deceleration power supply 9 may besimultaneously activated to apply the acceleration electrode 2 and thedeceleration electrode 3 with an acceleration voltage and a decelerationvoltage, respectively. In this case, since the sum of the voltagesgenerated by the acceleration power supply 8 and the deceleration powersupply 9 is applied across the acceleration electrode 2 and thedeceleration electrode 3, a larger short-circuiting current can begenerated, thereby making it possible to remove particles in a shortertime.

According to the present invention, since the voltages of the ion sourcepower supplies are applied in such an order that the decelerationvoltage is applied after or simultaneously with the application of theacceleration voltage, it is possible to reduce the frequency of theoccurrence of breakdown in the ion source, which is problematic in anion beam processing apparatus or the like, particularly, the breakdownthat occurs due to particles attached on the electrodes inherent in theion source, to smoothly activate the ion source, and to realize a stableoperation of the apparatus such as reduced requirements for maintenanceoperations such as cleaning for the electrodes of the ion source or thelike, a higher reliability of the apparatus, an improved operatingefficiency of the apparatus, and so on.

What is claimed is:
 1. A method of operating an ion source for an ionbeam processing apparatus, said ion source including an arc powersupply, for applying a positive potential to an acceleration electrodeto extract an ion beam, and a deceleration power supply for applying anegative voltage to a deceleration electrode for preventing electronsfrom flowing into said ion source, wherein a gas is introduced into saidion source to produce a plasma from said gas, and an electric field isformed to extract ions within said plasma as an ion beam, said methodcomprising the steps of: applying a positive voltage by saidacceleration power supply to said acceleration electrode; andsubsequently applying a negative voltage by said deceleration powersupply to said deceleration electrode.
 2. A method of operating an ionsource according to claim 1, wherein said step of applying a positivevoltage is performed by an acceleration power supply having a firstcapacity, and said step of subsequently applying a negative voltage isperformed by a deceleration power supply having a second capacity thatis smaller than said first capacity.
 3. A method of operating an ionsource for an ion beam processing apparatus, said ion source includingan arc power supply, an acceleration power supply for applying forapplying a positive potential to an acceleration electrode to extract anion beam, and a deceleration power supply for applying a negativevoltage to a deceleration electrode for preventing electrons fromflowing into said ion source, wherein a gas is introduced into said ionsource to produce a plasma from said gas, and an electric field isformed to extract ions within said plasma as an ion beam, said methodcomprising: a first step of applying a negative voltage rapidly by saiddeceleration power supply to said deceleration electrode; and a secondstep, simultaneously with the first step, of rapidly applying a positivevoltage by said acceleration power supply to said accelerationelectrode.
 4. A method of operating an ion source according to claim 3,wherein said second step is performed by an acceleration power supplyhaving a first capacity, and said first step is performed by adeceleration power supply having a second capacity that is smaller thansaid first capacity.
 5. A method of operating an ion source for an ionbeam processing apparatus, said ion source including an arc powersupply, an acceleration power supply for applying an accelerationelectrode with a positive voltage to extract an ion beam, and adeceleration power supply for applying a deceleration electrode with anegative voltage for preventing electrons from flowing into said ionsource, wherein a gas is introduced into said ion source to produce aplasma from said gas, and an electric field is formed to extract ionswithin said plasma as an ion beam, said method comprising: a first stepof applying a negative voltage rapidly by said deceleration power supplyto said deceleration electrode after applying a positive voltage by saidacceleration power supply to said acceleration electrode; and a secondstep of applying a negative voltage by said deceleration power supply tosaid deceleration electrode simultaneously with application of apositive voltage rapidly by said acceleration power supply to saidacceleration electrode, said method selectively executing one of saidfirst step and said second step.
 6. A method of operating an ion sourceaccording to claim 5, wherein in each of said first and second steps,the positive voltage is applied by an acceleration power supply having afirst capacity, and the negative voltage is applied by a decelerationpower supply having a second capacity that is smaller than said firstcapacity.
 7. A method of operating an ion beam processing apparatus,said ion beam processing apparatus has an ion source and a processingchamber, said ion source including an arc power supply, for applying apositive potential to an acceleration electrode to extract an ion beam,and a deceleration power supply for applying a negative voltage to adeceleration electrode for preventing electrons from flowing into saidion source, wherein a gas is introduced into said ion source to producea plasma from said gas, and an electric field is formed to extract ionswithin said plasma as an ion beam, said processing chamber comprising aholder for holding a workpiece, a shutter for protecting said workpiecefrom being irradiated with ions and electrons, and a neutralizer forgenerating electrons for electrically neutralizing the surface of saidworkpiece, said method comprising: a first step of applying a positivevoltage by said acceleration power supply to said accelerationelectrode; a second step of applying a negative voltage by saiddeceleration power supply to said deceleration electrode after executingsaid first step; and a third step of starting said neutralizer afterexecuting said second step.
 8. A method of operating an ion beamprocessing apparatus according to claim 7, further comprising the stepof: inserting said shutter to protect said workpiece from beingirradiated with ions before executing said first step.
 9. A method ofoperating an ion beam processing apparatus according to claim 8, furthercomprising the step of: removing said shutter after executing said thirdstep.
 10. A method of operating an ion beam processing apparatusaccording to claim 7, further comprising the step of: processing saidworkpiece after executing said third step.
 11. A method of operating anion beam processing apparatus according to claim 7, wherein said firststep is performed by an acceleration power supply having a firstcapacity, and said second step is performed by a deceleration powersupply having a second capacity that is smaller than said firstcapacity.